Stuff I Find on the Internet (exercise-related)

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    Or become pregnant to check this in practice

    /silly humour mode OFF, time to bed!/


      I often experience frustration myself when reading scientific articles - some things just seem contrary to common sense but alas, that's the way the process works, at least for now. To address the pregnancy issue:

      Again, the basic premise of the article is to show that the paradigm "weak/insufficient core muscles = back pain" or "back pain = weak core" is not valid or at least not as important as the proponents of core stability (in the academic sense of the term in 2010) imply. That's why the author made an analysis of articles related to this specific idea. The article about sit-ups states in the abstract (the full article is not available for free, it was written in 1990):

      An attempt was made to determine the effect of pregnancy on the abdominal muscles and to correlate changes in abdominal muscles strength with low-back pain during pregnancy. The study included 328 women. Group A consisted of 164 pregnant women; group B consisted of 164 non-pregnant women. The race, age, height, weight, parity, profession, time devoted to physical fitness per week, abdominal length, and relation between the abdominal length to height were recorded. A detailed history relating to backache prior to and during pregnancy was obtained. Each woman was asked to perform a single sit-up. The results of the study indicate that about 10% of pregnant women develop severe low-back pain that interferes with daily life activities. About 49% of the non-pregnant women complained of LBP. The pain did not interfere with activities of daily living. During pregnancy, due to overstretching of the abdominal muscles, the ability to perform a sit-up is significantly decreased. Whereas all non-pregnant women could perform a sit-up, 16.6% of pregnant women could not perform a single sit-up. There was no statistically significant correlation between the sit-up performance and backache. It may be concluded that during pregnancy the abdominal muscles become insufficient.
      What Lederman takes from this (and other examples, including the other study of pregnant women) is that there are clearly people whose abdominal wall muscles (TvA, obliques, rectus) are severely elongated and thus unable to provide sufficient force to move the trunk in supine position (not even enough to perform a single sit-up) and yet not all of them experience back pain. In that particular study, 90% of pregnant women did NOT experience LBP despite having weakened muscles and 51% percent of women with normal musculature DID experience it. In the other study, the women were excluded (they didn't drop out, I misstated that) because their condition improved while the muscles were still recovering and were unable to "stabilise" the spine. So the issue of not having a weight in the front anymore or taking care of the baby is not relevant in the scope of this article or original research (but I'm sure has implications in real life), what is relevant is that "weak core muscles per se do NOT cause back pain" or at least that the relationship is not straightforward. The research of women who had one part of rectus removed for reconstruction after mastectomy (meaning a part of their abdominals was actually missing, making the overall "core" less strong) similarly showed that they did not develop LBP even years after the operation.

      What I meant by "private coaches" is that they were probably not medical professionals working in state-run settings or covered by insurance. I know the situation is different in the USA but in other countries (he comes from the UK), people with back pain are usually referred to insurance-covered medical professionals (not fitness trainers) who must follow accepted protocols within their field and can't "dig up" alternative approaches on the internet or they can have their licenses revoked. They also often lack the time to treat people individually and must prepare programs to fit a variety of people with different conditions (group exercise). I am a member of several groups related to this field on social media and I have observed that the literature the students/practitioners use in professional rehabilitative science is largely outdated by standards of current fitness scene. The thing is, a single article, study or protocol, even if successful, is not implemented right away. Often, it takes years or even decades for it to be repeated, observed and if promising enough, included in new textbooks, curriculi and practice. It's not just rehabilitation - you often see research with tantalizing headlines (cure for cancer, new operation procedures etc.) and expect it to be used right away but it is in fact years away from being implemented worldwide. The training of martial artists and boxers is not relevant in this aspect I think, whether new or old - their goal is not to treat back pain after injury or disease (herniated discs, end-plate fractures, vertebral fractures, soft tissue damage etc.) but increase strength in that area to produce great force in their punches/kicks, to endure long training sessions and resist hard and fast blows to the abdomen.

      It was a nice exchange.


        I think we're just not speaking the same language right now, something is lost in translation

        I will try once more.

        Title: The Myth of Core Stability
        Dr. Eyal Lederman

        Core stability, transverses
        abdominis, chronic lower back

        and neuromuscular rehabilitation
        The principle of core stability has gained wide acceptance in
        training for prevention of injury and as a treatment modality
        for rehabilitation of various musculoskeletal conditions in
        particular the lower back. There has been surprising little
        criticism of this approach up to date. This article will reexamine the original findings and the principles of core
        stability and how well they fare within the wider knowledge
        of motor control, prevention of injury and rehabilitation of
        neuromuscular and musculoskeletal systems following injury.
        How essential is TrA for spinal stabilisation? One way to asses this is to look at situations
        where the muscle is damaged or put under abnormal mechanical stress. Would this
        predispose the individual to lower back pain?
        Pregnancy is another state that raises some important questions about the role of TrA or
        any abdominal muscle in spinal stabilisation.
        Now that'a a very general statement, ANY abdominal muscle. Does he mean ANY of the muscles you mention in your sentence about professionals understanding core a group of muscles?

        Ann-Core said:
        "Core" muscles are usually interpreted as the deep muscles of the back (multifidi, erectores spinae, sometimes quadratus lumborum) and the abdomen (TvA, external, internal obliques and rectus abdominis). In popular culture, "core" is often reduced to "six-pack".
        So if he is a professional we should assume that he understands the word CORE as encompassing all of the above, plus perhaps also serratus anterior. It is in popular culture that the core is reduced to the six pack, so mostly rectus abdominus. Now let's have a look at this fragment about pregnant women again:

        It would be interesting
        to see how these individuals stabilise their trunk and whether they suffer more back pain.
        Pregnancy is another state that raises some important questions about the role of TrA or
        any abdominal muscle
        in spinal stabilisation. During pregnancy the abdominal wall
        muscles undergo dramatic elongation, associated with force losses and inability to
        stabilise the pelvis against resistance [11, 12]. Indeed, in a study of pregnant women
        (n=318) they were shown to have lost the ability to perform sit-ups
        due to this extensive
        elongation and subsequent force losses [12].
        So first he talks about TrA (also called TA or TVA) or ANY abdominal muscle, but the only example that is given is about sit-ups, which is mostly about rectus abdominus (as you said, mistakenly taken as core in popular culture).

        Can it be a serious study about core stability during pregnancy if there is no mention about internal and external obliques or serratus anterior? They also play a big role in stabilizing the trunk.

        I am sorry but this is not a thorough approach. It's just licking the surface and yet it is used as an argument and apparently a solid one.

        I will repeat it, doing a sit-up has little to do with overall core stability and if a professional whose daily work evolves around this topic writes a paper where he easily jumps from TrA to rectus abdominus to core understood more widely then it is simply confusing. That was my point.

        And I will repeat it, too: doing a sit-up during pregnancy is not only related to strength levels per se, but also to ligament pain or discomfort. that's why most women were able to do a sit-up, only 16.6% were not able to do even one. They may have been experiencing not only muscle weakness, but also other symptoms (ligament pain being probably the biggest reason). that's why you cannot use this factor. Or at least it shouldn't be used as a conclusive one.

        His conclusion is that this proves that LBP is not caused by weak core, because when you have a weak core you cannot do a sit up, and yet women who could not do a sit-up had no LBP.

        It's not about studies, it's not about certificates, it's about logic.

        His conclusion is not logical.

        You can be unable to do a sit-up and yet have quite strong abdominal muscles (except rectus abdominus which undergoes the most of the elongation process). In the begininng he talks about ANY abdominal muscle being useful (or not) in stabilising the spine and thus preventing lower back pain.

        But in reality he talks only about some of these muscles. This is not a thorough study this way.

        I just wanted to clarify this.

        Other than that, I stated this in several points in my first messages, I do agree with him on many aspects.


          inbetween, if you are upset about the sit-up study, you have to take it out on original researchers, not Lederman. He didn't design or do that study and he is not saying that sit-ups are a measure of core strength or stability - and the authors of the study actually expressly say that in the article. The only thing he takes away from it, and this is the same conclusion that the original researchers came to and have written it also in the abstract I posted above, is that back pain and abdominal weakness are not/are weakly correlated according to results of this particular study. I think it would be good if you look up the original research and their caveats (e.g. there were 4 categories of sit-ups, the least demanding one only requiring the lift of head, shoulders and upper torso 40 degrees from the support etc.) - If the link doesn't work, type the title " Low-Back Pain in Pregnancy: Abdominal Muscles, Sit-up Performance, and Back Pain" into Sci-Hub.

          The paragraph where all these studies are mentioned is called "Assumptions about stability and the role of TrA muscle" and he argues that the role of TrA as a spinal stabiliser is overstated while also arguing against "core stability" muscles as such and their important role in LBP.

          In essence the passive human spine is an unstable structure and therefore further stabilisation is provided by co-contraction of trunk muscles. Erroneously, these muscles are often referred to in CS approach as the “core” muscles, assuming that there is a distinct group, with an anatomical and functional characteristics specifically designed to provide for the stability. One of the muscles in this group to have received much focus is TrA. It is widely believed that this muscle is the main anterior component of trunk stabilisation. It is now accepted that many different muscles of the trunk contribute to stability and that their stabilising action may change according to varying tasks (see further discussion below).

          The TrA has several functions in the upright posture. Indeed stability, but this function is in synergy with every other muscle that makes up the abdominals wall and beyond [6-8]. It acts in controlling pressure in the abdominal cavity for vocalization, respiration, defecation, vomiting etc. [9]. TrA forms the posterior wall inguinal canal and where its valve-like function prevents the viscera from popping out through the canal [10].
          How essential is TrA for spinal stabilisation? One way to asses this is to look at situations where the muscle is damaged or put under abnormal mechanical stress. Would this predispose the individual to lower back pain?
          He uses the following to elaborate on this:
          • TvA is absent or fused to the internal oblique as a normal variation (he doesn't have data on whether this impacts LBP but the fact that it's not that uncommon and considered a normal variation is significant)
          • The sit-up study
          • Study of LBP post-partum
          • Literature on obesity (distention of abdominal muscles) and weak association with LBP
          • Rectus abdominis removed during mastectomy study
          He then suggests a further study of incidence of LBP among patients who had inguinal hernia repair because TvA is affected during this procedure - up to 2010 no studies were done on this subject (and if there was significant correlation between the two, someone would have most likely checked this because inguinal hernia is quite a common and routine operation and there woud have been reason to improve the procedure or rehab). Then he concludes:

          We can conclude from the above that healthy abdominal musculature can demonstrate dramatic physiological changes, such as during pregnancy, post-partum and obesity, with no detriment to spinal health. Similarly, damage to abdominal musculature does not seem to impair normal movement or contribute to LBP.
          He also lists at least 5 additional pregnancy/LBP studies in the references, but I haven't checked them yet.

          Pregnancy is another state that raises some important questions about the role of TrA or any abdominal muscle in spinal stabilisation.
          I don't see how this is a general or somehow inaccurate/confusing statement. The abdominal muscles are just the four, TvA, rectus and both obliques (serratus anterior is usually in the deep chest/upper back category, not abdomen). They form the abdominal wall and all get elongated during pregnancy, not just rectus abdominis and they also work in unison in all abdominal movements (to varying degree of course).

          You are entitled to believe that this article is confusing, inaccurate, using poor references or outdated but I don't find such fault in it. I'm wondering if you are more upset with the concepts (and your different/updated understanding of them) than with the author himself. And yes, I'm sure if we talked in person some things would be a lot clearer for both of us.

          Here are some further studies on the subject of "core"/LBP (mostly from the period pre-2010), if you ever have the time and if you are still interested in this article and the validity of Lederman's conclusions (brief article review & synopsis):


            No, I am not upset with the author himself and yes, I would love to talk about it in real life because I have a crazy schedule waiting ahead and I will not find more time to explain things further by typing and always missing several thoughts in the process, aghh internet frustrations

            Thank you for this interesting exchange and as always in such circumstances I really wish we could have better means of communication than just written word.

            Have a lovely rest of the week and let's leave this thread for even more interesting articles!!!Keep posting them!